U.S. patent application number 14/251760 was filed with the patent office on 2014-12-11 for magneto-elastic sensor, load pin, ball-joint and tow coupling comprising this sensor, method of determining a direction of a load vector.
This patent application is currently assigned to Methode Electronics Malta Ltd. The applicant listed for this patent is Methode Electronics Malta Ltd. Invention is credited to Johannes GIE IBL.
Application Number | 20140360282 14/251760 |
Document ID | / |
Family ID | 48092825 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140360282 |
Kind Code |
A1 |
GIE IBL; Johannes |
December 11, 2014 |
Magneto-Elastic Sensor, Load Pin, Ball-Joint And Tow Coupling
Comprising This Sensor, Method Of Determining A Direction Of A Load
Vector
Abstract
A magneto elastic sensor having a longitudinally extending shaft
like member which is subject to a load, is provided. A
magneto-elastically active region is directly or indirectly
attached to or forming a part of the member in such a manner that
the mechanic stress is transmitted to the active region. A
magnetically polarized region of the active region becomes
increasingly helically shaped as the application stress increases.
A magnetic field sensor means is arranged approximate the at least
one magneto elastically region for outputting a signal
corresponding to a stress induced magnetic flux emanating from the
magnetically polarized region. The magnetic sensor means is
configured for determination of a shear stress and/or of a tensile
or compressive stress. In particular, the sensor means comprises at
least one direction sensitive magnetic field sensor, which is
arranged having a predetermined and fixed spatial coordination with
the member.
Inventors: |
GIE IBL; Johannes; (Mriehel,
MT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Methode Electronics Malta Ltd |
Mriehel |
|
MT |
|
|
Assignee: |
Methode Electronics Malta
Ltd
Mriehel
MT
|
Family ID: |
48092825 |
Appl. No.: |
14/251760 |
Filed: |
April 14, 2014 |
Current U.S.
Class: |
73/779 ; 280/511;
403/27 |
Current CPC
Class: |
F16C 11/06 20130101;
G01L 9/0001 20130101; G01L 3/102 20130101; G01L 1/125 20130101;
G01N 27/72 20130101; G01P 13/02 20130101; Y10T 403/20 20150115;
B60D 1/248 20130101 |
Class at
Publication: |
73/779 ; 280/511;
403/27 |
International
Class: |
G01L 9/00 20060101
G01L009/00; B60D 1/24 20060101 B60D001/24; F16C 11/06 20060101
F16C011/06; G01N 27/72 20060101 G01N027/72; G01P 13/02 20060101
G01P013/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 15, 2013 |
EP |
13 163 832.2 |
Claims
1. A magneto-elastic sensor comprising: a longitudinally extending
shaft like member, which is subject to a load introducing mechanic
stress in the member, at least one magneto-elastically active
region directly or indirectly attached to or forming a part of the
member in such a manner that the mechanic stress is transmitted to
the active region, said active region comprising at least one
magnetically polarized region such that the polarization becomes
increasingly helically shaped as the applied stress increases; a
magnetic field sensor means arranged approximate the at least one
magneto-elastically active region for outputting a signal
corresponding to a stress-induced magnetic flux emanating from the
magnetically polarized region; characterized in that the magnetic
sensor means comprising at least one direction sensitive magnetic
field sensor, which is configured for determination of a shear
stress and/or of a tensile or compressive stress, wherein the
magnetic field sensors are in particular arranged to have a
predetermined and fixed spatial coordination with the member.
2. The magneto-elastic sensor of claim 1, wherein the direction
sensitive magnetic field sensor is arranged in that a sensing
direction of the magnetic field sensor is at least substantially
parallel to a tangential direction of the shaft like member or in
that the sensing direction of the magnetic field sensor is at least
substantially parallel to a radial direction of the shaft like
member.
3. The magneto-elastic sensor of claim 1 or 2, wherein the magnetic
sensor means comprises a first and a second direction sensitive
magnetic field sensor having 180.degree. opposite sensing
directions.
4. The magneto-elastic sensor of claim 3, wherein the first and the
second magnetic field sensor are arranged approximate to opposite
sides of the magneto-elastically active region, respectively,
wherein said sides of the magneto-elastically active region are
opposite to each other with respect to the shaft axis.
5. The magneto-elastic sensor of any of the preceding claims,
wherein the sensor means comprises at least four magnetic field
sensors having a first to fourth sensing direction, wherein the
sensing directions and a shaft axis are at least substantially
parallel to each other, and wherein the first to fourth magnetic
field sensor are arranged along the circumference of the shaft
having substantially equal distances in circumferential direction
between each other.
6. The magneto-elastic sensor of claim 5, wherein the first and
third magnetic field sensor are arranged opposite to each other
with respect to the shaft axis and the first and third sensing
direction are arranged 180.degree. opposite to each other, and
wherein the second and fourth magnetic field sensor are arranged
opposite to each other with respect to the shaft axis and the
second and fourth sensing direction are arranged 180.degree.
opposite to each other.
7. The magneto-elastic sensor according to any of the preceding
claims, wherein the member comprises a first magneto-elastically
active region and a second magneto-elastically active region, which
are directly or indirectly attached to or form a part of the member
in such a manner that the mechanic stress is transmitted to the
active regions, each active region comprising a magnetically
polarized region, wherein the magnetic polarization of the first
active region and the magnetic polarization of the second active
region are substantially opposite to each other, and wherein the
magnetic sensor means comprises a first pair of magnetic sensors
comprising a first and a second magnetic field sensor being
arranged approximate the first magneto-elastically active region
for outputting a first signal corresponding to a stress-induced
magnetic flux emanating from the first magnetically polarized
region and the magnetic sensor means comprises a second pair of
magnetic sensors comprising a first and a second magnetic field
sensor being arranged approximate the second magneto-elastically
active region for outputting a second signal corresponding to a
stress-induced magnetic flux emanating from the second magnetically
polarized region, wherein the magneto-elastic sensor further
comprises a control unit, which is configured for determination of
the stress applied to the member by performing a differential
evaluation of the signals of the first pair of sensors and the
second pair of sensors.
8. The magneto-elastic sensor of any of the previous claims,
wherein the member is an at least partially hollow shaft and all
magnetic field sensors of the sensor means are entirely arranged
inside the interior of the hollow shaft.
9. The magneto-elastic sensor of any of the previous claims,
wherein the at least one magneto-elastically active region projects
along a circumference of the member, and wherein said region is
magnetized in that the domain magnetizations in the magnetically
polarized region lie within at most a plus or minus 45.degree.
limit of a circumferential direction of the member.
10. A load pin having a longitudinally extending shaft like member
incorporating a magneto-elastic sensor of any of the preceding
claims.
11. A ball-joint having bearing stud and socket, the bearing stud
comprises a longitudinally extending shaft like member
incorporating a magneto-elastic sensor according to anyone of
claims 1 to 9.
12. A tow coupling having a curved shaft and a tow-ball, the curved
shaft comprising at least one longitudinally extending shaft like
member incorporating a magneto-elastic sensor according to anyone
of claims 1 to 9, in particular the curved shaft comprises a first
and a second longitudinally extending shaft like member, the shaft
axis of which is substantially perpendicular to each other, wherein
the first and the second longitudinally extending shaft like member
each incorporate a magneto-elastic sensor according to anyone of
claims 1 to 9.
13. A method of determining a direction of a load vector, the
method comprising the steps of: providing a magneto-elastic sensor
comprising: a longitudinally extending shaft like member, which is
subject to the load introducing mechanic stress in the member; at
least one magneto-elastically active region directly or indirectly
attached to or forming a part of the member in such a manner that
the mechanic stress is transmitted to the active region, said
active region comprising at least one magnetically polarized region
such that the polarization becomes increasingly helically shaped as
the applied stress increases; a magnetic field sensor means
arranged approximate the at least one magneto-elastically active
region for outputting a signal corresponding to a stress-induced
magnetic flux emanating from the magnetically polarized region;
wherein the magnetic sensor means comprises at least one direction
sensitive magnetic field sensor, which is arranged to have a
predetermined and fixed spatial coordination with the member,
exposing the longitudinally extending shaft like member to the
load, processing measurement data of the at least one direction
sensitive magnetic field sensor so as to determine a shear stress
and/or of a tensile or compressive stress, in particular so as to
determine a direction of the load vector from the measurement data
and the predetermined and known spatial coordination between the
direction sensitive magnetic field sensor and the member.
14. The method for determining a direction of a load vector of
claim 13, wherein the sensor means comprises at least a first to
fourth magnetic field sensor having a first to fourth sensing
direction, wherein the sensing directions and a shaft axis are at
least substantially parallel to each other, and wherein the first
to fourth magnetic field sensor are arranged along the
circumference of the shaft having substantially equal distances in
circumferential direction between each other, the method further
comprising the steps of: processing measurement data of the first
and third magnetic field sensor so as to determine a first
component of a load vector and processing measurement data of the
second and fourth magnetic field sensor so as to determine a second
component of the load vector, determining a direction of the load
vector, which impacts the longitudinally extending shaft like
member, from the determined first and second component and the
predetermined and known spatial coordination of the first to fourth
magnetic field sensor with respect to the member.
15. The method for determining a direction of a load vector of
claim 13 or 14, wherein the member comprises a first
magneto-elastically active region and a second magneto-elastically
active region, which are directly or indirectly attached to or form
a part of the member in such a manner that the mechanic stress is
transmitted to the active regions, each active region comprising a
magnetically polarized region, wherein the magnetic polarization of
the first active region and the magnetic polarization of the second
active region are substantially opposite to each other, and wherein
the magnetic sensor means comprises a first pair of magnetic
sensors comprising a first and a second magnetic field sensor being
arranged approximate the first magneto-elastically active region
for outputting a first signal corresponding to a stress-induced
magnetic flux emanating from the first magnetically polarized
region and the magnetic sensor means comprises a second pair of
magnetic sensors comprising a first and a second magnetic field
sensor being arranged approximate the second magneto-elastically
active region for outputting a second signal corresponding to a
stress-induced magnetic flux emanating from the second magnetically
polarized region, the method further comprising the step of:
performing a differential evaluation of the signals of the first
pair of sensors and the second pair of sensors so as to determine
the stress applied to the member.
Description
FIELD OF THE INVENTION
[0001] The invention is related in general to systems and methods
involving the use of magnetic field sensors for measuring a load.
In particular, the invention is related to a magneto-elastic
sensor, a load pin, a ball joint and a tow coupling incorporating
this sensor. Furthermore, the invention relates to a method of
determining a direction of a load vector.
DESCRIPTION OF THE RELATED ART
[0002] In the control of systems having a member, which is subject
to mechanic forces, the determination of the mechanic load is one
of the fundamental parameters of interest. The sensing of the load,
the torque, bending, and/or shear stress should be performed in an
accurate, reliable and inexpensive manner.
[0003] Previously, the measurement of mechanic load was
accomplished using contact-type sensors, which are directly
attached to the member or are incorporated in said member. A
typical contact-type sensor is a strain-gauge. This detector is
directly attached to a surface of the member or is incorporated in
the member. For example, a strain-gauge is attached to a surface of
a shaft. The electrical resistance of this device changes, when the
strain-gauge undergoes a certain strain.
[0004] A typical application of a strain-gauge is a load pin, which
is a transducer used to measure load and force and to provide
overload protection. The load pins may be mounted into machines in
place of normal shafts. They are typically fitted with
strain-gauges, allowing them to produce a signal proportional to
the measured load.
[0005] However, strain-gauges are relatively unstable and offer a
limited reliability due to the necessary direct mechanical contact
with the member taking up the load. In addition to this, the
measurement values of strain-gauges tend to drift, thereby limiting
the reliability, in particular for long term measurements.
[0006] As an alternative to the widely used strain-gauges,
non-contact type sensors exploiting the magneto-elastic effect were
developed. These are frequently applied for torque measurements at
rotating shafts in various mechanic systems. For example, U.S. Pat.
No. 6,553,847 B2 of Garshelis, the disclosure of which is
incorporated herein by reference in its entirety, discloses a
magneto-elastic torque sensor, which provides an output signal
indicative of the applied torque. Another sensor for measuring the
torque, which is applied to a rotating shaft, is disclosed in U.S.
Pat. No. 5,351,555 of Garshelis, the disclosure of which is
incorporated herein by reference in its entirety. In the U.S. '555
patent, the magneto-elastically active region resides in an annular
member surrounding the shaft. This annular member comprises
magnetic material endowed with an effective uniaxial magnetic
anisotropy in circumferential direction. When the shaft is subject
to a torque, the stress induced in the shaft is transferred to the
annular member, which is rigidly connected to the shaft. In the
U.S. '847 patent, the material of the shaft itself is magnetically
polarized in circumferential direction. Therefore, this sensor
dispenses with the separate ring comprising the magnetic material.
Within both systems, the magnetic field sensors are mounted
proximate to the magnetoelasticly active region, in order to sense
the magnetic field emanating from this region. Upon application of
a torsional stress to the shaft, the circumferentially directed
magnetization reorients and becomes increasingly helical as the
torsional stress increases.
[0007] U.S. Pat. No. 2012/0074933 A1, the disclosure of which is
incorporated herein by reference in its entirety, discloses a
non-contact sensor of the magnetoelasticly type comprising a
plurality of sensors, which are arranged around the circumference
of a shaft. The magnetic field sensors are stationary while the
shaft is rotating. As a result, each sensor is repeatedly exposed
to the magnetic field emanating from a certain area of the
magnetically polarized region. This provides an averaging effect to
the measurement value of the strain. This is because for
determination of the value of the strain, the signals of the
individual sensors are averaged. Thus, residual inhomogeneities of
the magnetic polarization are averaged out.
[0008] In summary, all prior art concepts either apply conventional
strain-gauges or have one or more static magnetic field sensors
cooperating with a rotating shaft comprising the magnetically
polarized region.
[0009] Based on the foregoing, there is a need for a new and better
technique for effectively measuring stress and strain in systems
having a member, which is typically non-rotating, but which is
subject to a mechanic load.
SUMMARY
[0010] In one aspect of the invention, a magneto-elastic sensor
comprising a longitudinally extending shaft like member having at
least one magneto-elastically active region and a magnetic field
sensor means is provided. The longitudinally extending shaft like
member is subject to a load introducing mechanic stress in said
member. The at least one magneto-elastically active region is
directly or indirectly attached to the shaft like member. However,
the at least one magneto-elastically active region may also form a
part of said member. The magneto-elastically active region is
arranged in such a manner that the mechanic stress is transmitted
to the active region. Said region comprises at least one
magnetically polarized region such that the magnetic polarization
becomes increasingly helically shaped as the applied stress
increases. The magnetic field sensor means is arranged approximate
the at least one magneto-elastically active region. The magnetic
field sensor means is further configured for outputting a signal
corresponding to a stress-induced magnetic flux, which emanates
from the magnetically polarized region. The sensor according to
aspects of the invention comprises a magnetic sensor means
comprising at least one direction sensitive magnetic field sensor.
This direction sensitive magnetic field sensor is configured for
determination of a shear stress and/or of a tensile or compressive
stress. In particular, the direction sensitive magnetic field
sensor is arranged to have a predetermined and fixed spatial
coordination with the member.
[0011] Advantageously, the magneto-elastic sensor according to
aspects of the invention dispenses with a mechanical linkage or
connection between the sensor means and the shaft member. This
eliminates sources of error, which result from mechanic failure of
this connection. The sensor reliably operates even under extreme
operating conditions. The drift of the measurement values during
long term measurement is reduced. The sensor according to aspects
of the invention is versatile in that it may be applied to or
integrated in nearly every shaft like member, which may be for
example a part of a hydraulic unit of a land-, marine-, rail- or
air transport vehicle.
[0012] According to an advantageous embodiment of the invention,
the sensing direction of the at least one direction sensitive
magnetic field sensor is arranged in that the sensing direction is
at least substantially parallel to a tangential direction of the
shaft like member. The magneto-elastically active region, when
exposed to a normal force, emanates a stress induced magnetic flux
having a component directed in tangential direction of the shaft.
In conventional sensor systems, which exploit the magneto-elastic
effect, the tangential component of the magnetic field vector is
neglected. This is mainly due to the fact that these traditional
sensors are torque sensors measuring shear stress. In this
situation, the torque induced magnetic field vector is
substantially parallel to an axial direction of the shaft. However,
the magneto-elastic sensor according to aspects of the invention
senses the tangential component of the magnetic field vector and is
therefore capable of determining normal stress, which may be a
tensile or compressive stress in the shaft like member. This type
of stress may be due to bending of the shaft or exposure to an
axial load. In other words, the tensile and compressive stress is
preferably due to forces, which are applied substantially in axial
direction of the shaft.
[0013] According to another embodiment of the invention, the at
least one magnetic field sensor of the magnetic sensor means is
arranged in that the sensing direction of said sensor is at least
substantially parallel to a radial direction of the shaft like
member. The radial component of the stress induced magnetic field
evolves from all stress types, which are induced in the shaft like
member. In other words, shear stress and normal stress both induce
a magnetic field vector emanating from the active region, said
field vector having a radial component. Consequently, the
magneto-elastic sensor according to this particular embodiment of
the invention is sensitive to all stress types. The embodiment is
particularly suitable, if the shaft is exposed to only one single
type of stress.
[0014] According to still another embodiment of the invention, the
magnetic sensor means comprises a first direction sensitive
magnetic field sensor and a second direction sensitive magnetic
field sensor. The first and the second sensor are arranged in that
they have 180.degree. opposite sensing directions. This "vice
versa" configuration of the magnetic field sensors enables the
magneto-elastic sensor according to this embodiment to distinguish
between the different directions of the applied stress and mechanic
load. For example, compressive and tensile stresses are
distinguishable, if the measurement data, which is acquired from
the first and the second sensor, is differentially processed.
[0015] In another embodiment of the invention, the first and the
second magnetic field sensor are arranged approximate to opposite
sides of the magneto-elastically active region, respectively. These
sides of the active region are opposite to each other with respect
to the shaft axis. A side of the active region may be an interior
surface or wall of the shaft as well as an exterior wall or surface
of the shaft like member. This depends on the particular
configuration of the sensor means. When, for example, the sensors
of the sensor means are arranged in the interior of a hollow shaft
like member, the sides will be opposite surfaces of the cavity
inside the member. When the sensors are arranged exterior to the
shaft like member, opposite sides are the outer surfaces of the
shaft, which are opposite with respect to the shaft axis. In this
particular sensor arrangement, the sensor means is suitable for
acquiring stresses and loads in axial direction of the shaft, i.e.
tensile and compressive stress. Preferably, the first and the
second sensing direction may be arranged in that they are
substantially perpendicular to the shaft axis.
[0016] According to another advantageous aspect of the invention,
the magneto-elastic sensor comprises a sensor means having at least
four magnetic field sensors. These four sensors have a first to
fourth sensing direction. The first to fourth sensor are arranged
in that the first to fourth sensing direction and the shaft axis
are at least substantially parallel to each other. Furthermore, the
first to fourth magnetic field sensor is arranged along the
circumference of the shaft having substantially equal distances in
circumferential direction between each other. In particular, the
first and third magnetic field sensor is arranged opposite to each
other with respect to the shaft axis. The first and third sensing
direction may be arranged to be 180.degree. opposite to each other.
Furthermore, the second and fourth magnetic field sensor may be
arranged opposite to each other with respect to the shaft axis. The
second and fourth sensing direction may be arranged 180.degree.
opposite to each other.
[0017] According to this embodiment of the invention, the sensor
means is configured for determination of a first component and a
second component of the load, which is applied to the shaft like
member. In particular, the first and third magnetic field sensor
can form a first group of sensors and the second and fourth
magnetic field sensor can form a second group of sensors. If
considered in a Cartesian coordinate system, the first group of
sensors is suitable for determination of a load component, which is
directed along a first Cartesian axis, for example the X-axis. The
second group of sensors senses a component of the load, which is
substantially perpendicular to the first component. If this is
considered in the same Cartesian coordinate system, the second
group of sensors senses the force component in Y-direction. In
other words, the X- and Y-component of the load may be determined.
Consequently, the direction and the value of the stress or force,
which is applied to the shaft like member, may be determined from
said components for example in a Cartesian coordinate system.
[0018] According to still another aspect of the invention, the
shaft like member comprises a first magneto-elastically active
region and a second magneto-elastically active region. Similar to
the other embodiments of the invention, these are directly or
indirectly attached to or form a part of the member in such a
manner that the mechanic stress is transmitted to the active
regions. A respective one of the active regions comprises a
magnetically polarized region. The magnetic polarization of the
first active region is substantially opposite to the magnetic
polarization of the second active region. The magnetic sensor means
comprises a first pair of magnetic sensors and a second pair of
magnetic sensors. Each pair comprises a first and a second
direction sensitive magnetic field sensor. The sensors of the first
and second pair being arranged approximate the first and second
magneto-elastically active region, respectively. The first sensor
pair outputs a first signal corresponding to a stress-induced
magnetic flux emanating from the first magnetically polarized
region. Similarly, the second pair of magnetic field sensors
outputs a second signal corresponding to a stress-induced magnetic
flux emanating from the second magnetically polarized region. A
control unit of the magneto-elastic sensor is configured for
determination of the stress applied to the member. The control unit
performs a differential evaluation of the signals of the first pair
of sensors and the second pair of sensors.
[0019] The differential evaluation of the signals advantageously
doubles the signal, which is correlated with the applied stress.
Because the polarization of the first and second magnetically
active region is opposite to each other, theoretically possible
external fields are compensated. The magneto-elastic sensor
according to this embodiment is more sensitive and less susceptible
to errors.
[0020] According to an embodiment of the invention, the member is
an at least partially hollow shaft and all magnetic field sensors
of the sensor means are entirely arranged inside the interior of
the hollow shaft. This is advantageous, if there is limited
construction space around the shaft like member. Furthermore, the
magneto-elastic sensor is less susceptible to external fields
because of a shielding effect of the shaft. In particular, the at
least one magneto-elastically active region projects along the
circumference of the member. Said region is magnetized in that the
domain magnetizations in the magnetically polarized region lie
within at most a plus or minus 45.degree. limit of a
circumferential direction of the member. Furthermore, the direction
sensitive magnetic field sensors may be vector sensors. In
particular, the vector sensors may be one of a Hall-effect,
magneto-resistance, magneto-transistor, magneto-diode, MAGFET field
sensors or fluxgate magneto-meter. These aspects advantageously
apply to all embodiments of the invention.
[0021] The sensor according to aspects of the invention is
particularly suitable for incorporation in a load pin, a ball-joint
or in a tow coupling, which may be part of a land based on road or
off-road vehicle.
[0022] According to another aspect of the invention, a load pin
having a longitudinally extending shaft like member incorporating a
magneto-elastic sensor according to aspects of the invention is
provided. Conventionally, load pins are equipped with strain-gauges
having the well known technical deficiencies. The load pin
according to aspects of the invention overcomes the drawback of the
prior art solutions. In particular, the load pin does not tend to
drift of the measurement values and is less error-prone.
[0023] Any hydraulic piston, crane application, car and other
various applications incorporating bolts and pins, where shear
forces are applied, may be equipped with the load pin according to
aspects of the invention. Traditionally, shear force sensors using
strain-gauges are designed in that they get intentionally weaken to
provide enough deformation so as to allow a measurement of the
applied loads. The magneto elastic shear-force sensor, however,
provides the possibility to design the bolt without weaken
locations and significantly higher overload capability. The load
pin having the integrated magneto-elastic sensor provides the
possibility to detect shear forces in pins, screws, bolts etc.
[0024] According to still another aspect of the invention, a
ball-joint having a bearing stud and a socket, wherein the bearing
stud comprises a longitudinally extending shaft like member
incorporating a magneto-elastic sensor according to aspects of the
invention, is provided. Ball-joints are typically subject to forces
and stresses of various directions. The sensor according to aspects
of the invention is advantageously suitable for determination of
the direction of the force or stress, which is applied to the shaft
like member of the ball-joint. In stabilizer links and steering
systems, ball joints are used to connect moving components to
provide flexibility. The detection of loads within the ball joints
provides extended possibilities for future stability control
systems, in particular in chassis applications. The ball joint
having an integrated load sensor provides the possibility to detect
load on stabilizer links, steerings, etc.
[0025] According to still another aspect of the invention, a tow
coupling having a curved shaft and a tow ball is provided. The
curved shaft comprises at least one longitudinally extending shaft
like member incorporating a magneto-elastic sensor according to
aspects of the invention. Similar to the ball-joint, the tow
coupling is also subject to forces having various directions. The
determination of said forces may be suitable so as to accomplish
with safety requirements and for stability control. The detection
of the applied load on tow couplings is desirable within the
automotive industry. The magneto-elastic sensor according to
aspects of the invention provides the possibility to achieve the
recommended accuracies, cost targets and to fulfill environments
specifications.
[0026] According to an advantageous embodiment, the curved shaft of
the tow coupling comprises a first and a second longitudinal
extending shaft like member. The shaft axis of the first and the
second shaft like member are substantially perpendicular to each
other. The first and the second shaft like member are each provided
with a magneto-elastic sensor according to aspects of the
invention. In particular, these sensors may be incorporated in the
shaft like members. Advantageously, if two sensor systems are
integrated in the tow coupling, a supporting force and a towing
force may be detected. In addition to this, the corresponding
transverse forces may be determined.
[0027] According to still another aspect of the invention, a method
of determining a direction of a load vector is provided. Within
said method, a magneto-elastic sensor according to aspects of the
invention is provided. In other words, a sensor comprising a
longitudinally extending shaft like member is provided, wherein
said member is subject to the load introducing mechanic stress in
the member. Furthermore, the shaft like member comprises at least
one magneto-elastically active region, which is directly or
indirectly attached to or forms a part of the member. This active
region cooperates with the member such that the mechanic stress is
transmitted to the active region. Said active region comprises at
least one magnetically polarized region such that the polarization
becomes increasingly helically shaped as the applied stress
increases. A magnetic field sensor means is arranged approximate
the at least one magneto-elastically active region. This is
configured for outputting a signal corresponding to a stress
induced magnetic flux emanating from the magnetically polarized
region. The magnetic sensor means further comprises at least one
direction sensitive magnetic field sensor. The magnetic field
sensor is configured for determination of a shear stress and/or of
a tensile or compressive stress. In particular, the magnetic field
sensor is arranged to have a predetermined and fixed spatial
coordination with the member.
[0028] Furthermore, within the method according to aspects of the
invention, the longitudinally extending shaft like member is
exposed to a load. Measurement data of the at least one direction
sensitive magnetic field sensor is processed so as to determine a
shear stress and/or of a tensile or compressive stress. In
particular, a direction of the load vector may be determined from
the measurement data on the one hand and the predetermined and
known spatial coordination between the magnetic field sensor and
the member on the other hand.
[0029] According to an advantageous embodiment of the invention,
the sensor means comprises at least a first to fourth magnetic
field sensor having a first to fourth sensing direction. The
sensing directions and the shaft axis are at least substantially
parallel to each other. The first to fourth magnetic field sensor
is arranged along the circumference of the shaft having
substantially equal distances in circumferential direction between
each other. The method according to this embodiment of the
invention further incorporates processing of measurement data of
the first and third magnetic field sensor so as to determine a
first component of the load vector. Furthermore, the method
incorporates processing of measurement data of the second and
fourth magnetic field sensor so as to determine a second component
of the load vector. A direction of the load vector is determined
from the first and second component and the predetermined and known
spatial coordination of the first to fourth magnetic field sensor
with respect to the member.
[0030] In another embodiment of the invention, a magneto-elastic
sensor is provided having a member, which comprises a first
magneto-elastically active region and a second magneto-elastically
active region. These are directly or indirectly attached to or form
a part of the member in such a manner that the mechanic stress is
transmitted to the active regions. Each active region comprises a
magnetically polarized region, wherein the magnetic polarization of
the first active region and the magnetic polarization of the second
active region are substantially opposite to each other. The
magnetic sensor means comprises a first pair of magnetic sensors
comprising a first and a second magnetic field sensor being
arranged approximate the first magneto-elastically active region.
This first pair outputs a first signal corresponding to a
stress-induced magnetic flux emanating from the first magnetically
polarized region. The magnetic sensor means further comprises a
second pair of magnetic sensors comprising a first and a second
magnetic field sensor. These are arranged approximate the second
magneto-elastically active region for outputting a second signal.
This second signal corresponds to a stress-induced magnetic flux
emanating from the second magnetically polarized region. A
differential evaluation of the two signals, i.e. of the first pair
of the sensors and the second pair of sensors, is performed. The
stress, which is applied to the member, is determined from this
differential measurement and the corresponding evaluation.
[0031] Same or similar advantages which have been already mentioned
with respect to the magneto-elastic sensor according to aspects of
the invention apply in a same or similar way to the method of
determining a direction of the load vector and will be not
repeated.
BRIEF DESCRIPTION OF DRAWINGS
[0032] Further aspects and characteristics of the invention ensue
from the following description of the preferred embodiments of the
invention with reference to the accompanying drawings, wherein
[0033] FIG. 1A shows a simplified side view of a magneto-elastic
sensor configuration according to embodiments of the invention,
[0034] FIG. 1B shows a simplified cross sectional view of a
magneto-elastic sensor configuration according to embodiments of
the invention,
[0035] FIG. 2A shows a simplified side view of a magneto-elastic
sensor configuration according to embodiments of the invention,
[0036] FIG. 2B shows a simplified cross sectional view of a
magneto-elastic sensor configuration according to embodiments of
the invention,
[0037] FIG. 3A shows a simplified side view of a magneto-elastic
sensor configuration according to embodiments of the invention,
[0038] FIG. 3B shows a simplified cross sectional view of a
magneto-elastic sensor configuration according to embodiments of
the invention,
[0039] FIG. 4A shows a simplified axial cross section view of a
magneto-elastic sensor configuration according to embodiments of
the invention,
[0040] FIG. 4B shows a simplified cross sectional view of a
magneto-elastic sensor configuration according to embodiments of
the invention,
[0041] FIG. 5A shows a simplified axial cross section view of a
magneto-elastic sensor configuration according to embodiments of
the invention,
[0042] FIG. 5B shows a simplified cross sectional view of a
magneto-elastic sensor configuration according to embodiments of
the invention,
[0043] FIG. 6A shows a simplified axial cross section view of a
magneto-elastic sensor configuration according to embodiments of
the invention,
[0044] FIG. 6B shows a simplified cross sectional view of a
magneto-elastic sensor configuration according to embodiments of
the invention,
[0045] FIG. 7 is a simplified axial cross section of a load pin,
according to an embodiment of the invention,
[0046] FIG. 8 is a cross section of this load pin,
[0047] FIG. 9 is a simplified cross section of a magneto-elastic
sensor according to an embodiment of the invention,
[0048] FIGS. 10 and 12 show simplified axial cross sections of a
ball joint, according to embodiments of the invention,
[0049] FIGS. 11 and 13 show cross sections along the cutting line
denoted X-X in FIG. 10 and cutting line XII-XII in FIG. 12,
respectively,
[0050] FIGS. 14 and 15 show simplified axial cross sections of tow
couplings, according to embodiments of the invention.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0051] FIG. 1 A) is a simplified side view of a magneto elastic
sensor 2 according to an embodiment of the invention. A rotating
shaft like member 4 is provided with a magneto-elastically active
region 6 having a circumferential polarization P, the direction of
which is indicated by an arrow. When the shaft 4 is subject to a
shear stress, which means for example that the shaft portion left
from the active region 6 is urged to in a first direction and the
shaft portion right from the active region 6 is subject to a
counteracting force urging the shaft in opposite direction, the
magnetic flux vector emanating from the active region 4 has a
component, which is directed in axial direction of the shaft 4. The
sensor L detects this component of the shear stress induced
magnetic field and outputs a signal S. A processing unit 8 is
configured to process this signal S so as to determine the stress,
which is applied to the shaft 4. The sensor L has a sensing
direction, which is substantially parallel to a shaft axis A shown
in a dash-dotted line. The simplified cross section of FIG. 1 B)
further illustrates the arrangement of the sensor L with respect to
the shaft 4.
[0052] When the shaft 4 is subject to a force, which does not
introduce a shear stress, for example: a bending force or a load in
axial direction, the configuration shown in FIG. 2 A) and FIG. 2 B)
is capable of determining this load. In FIG. 2 A), there is a
simplified side view showing a sensor 2, according to this
embodiment of the invention. The magneto elastic sensor 2 comprises
a longitudinally extending shaft like member 4, which is subject to
a load introducing a tensile or a compressive stress in the
magneto-elastically active region 6. The shaft 4 may be a rotating
or a non rotating part. For example, it may be a part of a pin or
bolt. However, the shaft like member 4 may also be a rotating part,
for example a transmission shaft. The polarization P of the active
region 6 becomes increasingly helically shaped as the applied
stress increases. In particular, a magnetic field emanating from
the magnetically polarized region of the active region 6 exhibits a
tangential component. This component of the stress induced magnetic
field vector is detected using the direction sensitive sensor L.
This sensor L may be arranged in a fixed spatial coordination with
respect to the shaft like member 4. For example, the shaft 4 and
the sensor L may have a timely constant spatial coordination with
respect to each other.
[0053] The direction sensitive sensor L outputs a signal S, which
is communicated to the processing unit 8. The measurement data of
the direction sensitive sensor L is processed in that the direction
and a value of the load is determined from the signal S and the
predetermined and known spatial coordination between the member 4
and the sensor L. The tensile and compressive stress, which is
applied in axial direction, is determined. The simplified cross
section of FIG. 2 B) further illustrates the spatial coordination
between the member 4 and the direction sensitive sensor L. The
sensing direction is parallel to a tangent of the shaft 4. In other
words, it is at least substantially perpendicular to the shaft axis
A.
[0054] In FIG. 3 A), there is another simplified side view of a
magneto-elastic sensor 2, according to another embodiment of the
invention. The shaft like member 4 is configured similar to the
embodiment of FIG. 2. However, the direction sensitive sensor L is
arranged to have a sensing direction, which is parallel to the
radius of the shaft 4. The simplified cross section of FIG. 3 B)
further illustrates the spatial coordination between the member 4
and sensor L.
[0055] The magneto-elastic sensor 2 according to this embodiment of
the invention is sensitive to all types of stress. The polarization
P of the active region 6 becomes increasingly helically shaped as
the applied stress increases. The stress induced magnetic field
vector includes a radial component. Said radial component of the
magnetic field vector is detected using the sensor L. The radial
orientation is applicable in situations or applications when only
one type of stress appears. This is a prerequisite for correct
interpretation of the signal S in the processing unit 8. Otherwise,
it might be impossible to distinguish between the different types
of stress, for example between a torque and a tensile or
compressive stress.
[0056] FIG. 4 A) shows another magneto elastic sensor 2, according
to an embodiment of the invention. FIG. 4 B) is the corresponding
cross section of this sensor 2. The shaft like member 4 is a hollow
shaft, wherein the sensor L is arranged inside an interior space of
the shaft 4. The sensing direction of the sensor L is parallel to
the shaft axis A. The signal S of the sensor L is communicated to
the processing unit 8 using any suitable data link, for example a
wireless data link. Due to the axial orientation of the sensor L, a
torque and/or a shear stress, which is applied to the shaft 4, is
detectable. In particular, this embodiment is configured for
detection of a shear stress or force.
[0057] FIG. 5 A) is a simplified axial cross section of a
magneto-elastic sensor 2 comprising a hollow shaft like member 4
incorporating a direction sensitive sensor L, according to an
embodiment of the invention. The magnetic field sensor L is
arranged in tangential direction with respect to the shaft 4.
Similar to FIG. 2, the sensor 2 is suitable for measurement of
tensile or compressive stress, which is applied to the hollow shaft
4. This type of stress may be due to bending of the shaft 4.
Furthermore, the shaft 4 may be subject to a shear force. A force,
which is applied along the shaft axis A, can also introduce a
tensile or compressive stress. FIG. 5 B) is the simplified cross
section, which corresponds to FIG. 5 A). The output signal S is
communicated from the sensor L to the processing unit 8 for example
via a wireless data link. The shaft 4 may be a non rotating part,
such as a bolt for example, or it may be a rotating part, for
example a torque transmitting shaft.
[0058] FIG. 6 A) is another simplified cross section of a
magneto-elastic sensor 2, according to an embodiment of the
invention. FIG. 6 B) shows the corresponding cross section of this
sensor 2. Similar to the embodiment of FIG. 3, the sensor 2 of FIG.
6 is suitable for detection of any type of stress. This is due to
the radial orientation of the magnetic field sensor L.
[0059] FIG. 7 is a simplified cross section of a load pin 10
according to an embodiment of the invention. The load pin 10
comprises a first or upper member 11, which is coupled to a second
or lower member 12 via the shaft like member 4. The upper member 11
is subject to a first shear force FS1 pointing to the left. The
lower member 12 is exposed to a second and opposite shear force
FS2, pointing to the right. The shaft like member 4 comprises an
active region 6, which is arranged at the transition between the
upper and lower member 11, 12. Consequently, the active region 6 is
subject to shear forces causing the magnetic flux emanating from
the magnetically polarized region of said active region 6 to become
increasingly helically shaped, when the shear forces FS1, FS2
increase. The sensor means of the load pin 10 comprises four
direction sensitive magnetic field sensors LX1, LX2, LY1, LY2 being
arranged along the inner circumference of the shaft like member
4.
[0060] The configuration of the direction sensitive magnetic field
sensors LX1, LX2, LY1, LY2 is explained in more detail by making
reference to the simplified cross section of the load pin 10, which
is shown in FIG. 8. The cross sectional plane is arranged to be
substantially perpendicular to the shaft axis A. The first
direction sensitive sensor LX1 and the third direction sensitive
sensor LX2 form a first group of magnetic field sensors. The second
group of sensors consists of the second direction sensitive sensor
LY1 and the fourth direction sensitive sensor LY2. The sensing
direction SX1 of the first sensor LX1 is 180.degree. opposite to
the third sensing direction SX2 of the third sensor LX2. This is
indicated in the figure using the conventional signs. The first
sensing direction SX1 points out of the paper plane, the third
sensing direction SX2 points into the paper plane. Similar to the
first group of sensors LX1, LX2, the second sensing direction SY1
and the fourth sensing direction SY2 are 180.degree. opposite to
each other. The second and fourth sensor LY1, LY2 are arranged
accordingly. As it is indicated using the commonly known direction
signs, the second sensing direction SY1 points out of the paper
plane while the fourth sensing direction SY2 is directed into the
paper plane.
[0061] The second sensor LY1 having the second sensing direction
SY1 and the fourth sensor SY2 having the fourth sensing direction
SY2 are shown in the simplified cross section of FIG. 7. The first
sensor LX1 and the first sensing direction SX1 are added to the
simplified cross section of FIG. 7 solely for clarification of the
configuration of the sensors. Naturally, the first sensor LX1 is
not arranged in a common plane with the second and fourth sensor
SY1, SY2, as it is shown in the cross section of FIG. 8.
[0062] When the shaft like member 4 is exposed to the first and
second shear stress forces FS1, FS2, the signals of the first group
of sensors (comprising the first and the third sensor LX1, LX2) is
analyzed so as to determine a first component of a force F inducing
the respective shear stress forces FS1, FS2. In a Cartesian
coordinate system, this first component may be indentified with the
X-component FX of the applied force F. This is illustrated in FIG.
9). The evaluation of the measurement values of the sensors of the
second group (i.e. the second sensor LY1 and the fourth sensor LY2)
results in a value for a second component of the force F. Within
the same Cartesian coordinate system, this second force is
identified with the Y-component of the force F, i.e. the force
component FY.
[0063] Using the load pin 10 according to this embodiment of the
invention, the amount and the direction of an applied force F can
be determined. According to another embodiment of the invention
(not shown), the direction sensitive sensors have sensing
directions, which are substantially perpendicular to the shaft axis
A. This sensor configuration may be achieved by for example
selecting and rotating the first and third sensor SX1, SX2 by
90.degree. with respect to the shaft axis A. According to this
particular embodiment of the invention, the load pin 10 is suitable
for determination of a force introducing compressive or tensile
stress in axial direction.
[0064] FIG. 9 is a cross section of a magneto-elastic sensor 2
according to another embodiment of the invention. The first member
11 surrounds the second member 12, which is exposed to a force F.
The sleeve like first member 11 takes up the counteracting force,
which means that each side of the member 11 takes up a force of
F/2. The longitudinally extending shaft like member 4 intersects
the first and the second member 11, 12 along the shaft axis A. The
shaft like member 4 comprises a first magneto-elastically active
region 61 and a second magneto-elastically active region 62.
Similar to the other embodiments of the invention, these are
directly or indirectly attached to or form a part of the member 4
in such a manner that the mechanic stress is transmitted to the
active regions 61, 62. The active regions 61, 62 are magnetically
polarized in opposite direction. This is illustrated by the first
polarization P61 of the first active region 61 and the second
polarization P62 of the second active region 62. The magnetic
polarizations P61, P62 are substantially 180.degree. opposite to
each other. Furthermore, they are substantially perpendicular to
the shaft axis A.
[0065] A first pair of magnetic field sensors comprising a first
sensor L1 and a second sensor L2 is arranged inside the shaft like
member 4 in that this pair of sensors cooperates with the first
active region 61. Similar, a second pair of magnetic field sensors
comprising a first and a second sensor L1* and L2* is arranged
inside the shaft 4 so as to interact with the second active region
62. The sensors L1, L2 of the first pair and the sensors L1*, L2*
of the second pair are arranged approximate the first and the
second magneto-elastically active region 61, 62, respectively. The
first sensor pair L1, L2 outputs a first signal S, which is
illustrated as a voltage V varying with the applied force F in the
lower left of FIG. 9. The signal S corresponds to a stress-induced
magnetic flux emanating from the first magnetically polarized
region 61.
[0066] Similarly, the second pair of magnetic sensors L1*, L2*
outputs a second signal S* corresponding to a stress-induced
magnetic flux emanating from the second magnetically polarized
region 62. This signal S* is also a voltage V* varying with the
applied F (see lower right of FIG. 9). However, the slope of the
second signal S* is opposite to that of the first signal S. A
control unit (not shown) of the magneto-elastic sensor 2 is
configured for determination of the force F inducing a stress in
the member 4. The control unit performs a differential evaluation
of the signals S and S* of the first pair of sensors L1, L2 and the
second pair of sensors L1*, L2*. This differential evaluation
advantageously doubles the sensitivity of the signal, which is
correlated with the applied stress. Because the polarization P61
and P62 of the first and second magnetically active region 61, 62
is opposite to each other, theoretically possible external fields
are compensated. The magneto-elastic sensor 2 according to this
embodiment is more sensitive and less susceptible to errors.
[0067] Advantageously, all embodiment of the invention may be
equipped with the sensor configuration of FIG. 9 having separate,
oppositely polarized active regions 61, 62 and two corresponding
sets i.e. pairs of sensors L1, L2 and L1*, L2*.
[0068] Furthermore, the embodiment of FIG. 9 may be equipped with
the sensor configuration, which is known from the load pin in FIG.
8. In other words, the sensor pairs L1, L2 and L1*, L2* may be
replaced by a sensor configuration having four sensors LX1, LX2,
LY1, LY2, which is exemplarily shown in FIGS. 7 and 8. According to
this particular embodiment of the invention, additional force
vectors may be determined.
[0069] FIG. 10 is a simplified cross section of a ball-joint 20,
according to another embodiment of the invention. The ball-joint 20
comprises a socket 22 holding a bearing stud 24 having a shaft like
member 4 incorporating a sensor system. FIG. 11 is the
corresponding cross section along the plane X-X. When a force F is
applied to the ball-joint 20, the shaft like member 4 is subject to
various loads. The sensor system of the ball-joint 20 according to
the embodiment in FIGS. 10 and 11 is configured for shear stress
detection. In general, the shear stress detection operates similar
to the detection of the shear stress in the load pin of FIGS. 7 and
8.
[0070] The shaft like member 4 of the ball-joint 20 incorporates
four direction sensitive sensors LX1, LX2, LY1, LY2. Again, the
first and third magnetic field sensor LX1, LX2 form the first group
of sensors, which is for determination of the first component FX of
the applied force F (see FIG. 11). The second group of sensors,
which comprises the second and fourth direction sensitive magnetic
field sensor LY1, LY2, is configured for determination of the
second component FY of the applied force F. The sensing direction
(not shown) of the first to fourth sensor LX1, LX2, LY1, LY2 is
configured similar to FIG. 8. In other words, the sensing direction
of LX1 and LY1 point out of the paper plane. The sensing direction
of LY2 and LX2 point into the paper plane.
[0071] FIG. 12 and FIG. 13 illustrate a ball-joint 20 according to
another embodiment of the invention. FIG. 12 is a simplified axial
cross section along the plane XII-XII in FIG. 13. The sensor
system, which is incorporated in the shaft like member 4, comprises
a first to fourth direction sensitive magnetic field sensor L1, L2,
L1* and L2*. The direction sensitive sensors L1, L2, L1*, L2*are
tilted by 90.degree. with respect to the shaft axis A, when
compared to the sensors LX1, LX2, LY1 and LY2 of the embodiment in
FIGS. 10 and 11. The sensing directions of the magnetic field
sensors, only two of which are shown solely for clarity reasons
(see S1, S2 of the first and second sensor L1, L2), are
substantially perpendicular to the shaft axis A of the shaft like
member 4. Furthermore, the sensing directions of the sensor pairs
L1 and L2, i.e. S1 and S2 are 180.degree. opposite to each other.
Similarly, the sensing directions (not shown) of the second sensor
pair S1* and S2* are substantially 180.degree. opposite to each
other. This is further illustrated in the simplified cross section
of FIG. 13. Similar to the embodiment of FIG. 8, the sensor
arrangement in FIGS. 12 and 13 is configured for determination of
tensile and compressive stress in various directions. In other
words, the measurement values of the sensor pairs L1, L2 and L1*,
L2* may be evaluated so as to determined the component of the
stress vector.
[0072] The sensor system of the ball-joint 20 according to this
embodiment is configured for determination of an axial force F. Due
to the inverse sensing directions S1, S2 of the first and second
sensor L1, L2, the value and the prefix, i.e. the direction, of the
axially directed force F can be determined.
[0073] FIG. 14 is a simplified cross section showing a tow coupling
30, according to an embodiment of the invention. The tow coupling
30 comprises a curved shaft 32 carrying a tow ball 34. The shaft 32
of the tow coupling 30 incorporates a first shaft like member 4 and
a second shaft like member 4'. A respective one of the shaft like
members 4, 4' comprises a magneto-elastically active region 6, 6'
emanating a stress induced magnetic field vector, which is
detectable by a sensor arrangement. The first shaft like member 4
comprises a first and a second direction sensitive magnetic field
sensor L1, L2, which are configured for detection of a towing force
F. The first and second sensor L1, L2 in this first shaft like
member 4 are arranged in that their sensing directions (not shown)
are substantially parallel to the first shaft axis A.
[0074] The second sensor system, which is incorporated in the
second shaft like member 4', also comprises a first and a second
direction sensitive sensor L1', L2', both of which are arranged to
have a sensing direction (not shown), which is substantially
parallel to the second shaft axis A'. This second sensor system is
configured to detect a supporting force F' of the tow coupling
30.
[0075] The two sensor systems, which reside in the first and second
shaft like member 4, 4', respectively, can be equipped additional
sensors in that each system comprises four direction sensitive
magnetic field sensors. Such a sensor configuration is explained in
more detail with reference to FIGS. 7 and 8. When this
configuration is transferred to this embodiment, the corresponding
transverse forces of the force F and F' are also detectable.
[0076] In the simplified cross section of FIG. 15, there is another
embodiment of a tow coupling 30. The direction sensitive magnetic
field sensors L1, L2, L1', L2' are rotated by 90.degree. with
respect to the respective shaft axis A, A', when compared to the
embodiment of FIG. 14. The first and second direction sensitive
magnetic field sensor L1, L2 of the first sensor system, which is
arranged in the first shaft like member 4, have sensing directions
(not shown) which are preferably 180.degree. opposite to each other
and which are substantially perpendicular to the shaft axis A. The
second sensor system, which is incorporated in the second shaft
like member 4', comprises a first and second direction sensitive
magnetic field sensor L1', L2' having sensing directions, which are
preferably 180.degree. opposite to each other and which are
substantially perpendicular to the second shaft axis A'. The first
sensor system (i.e. the first and second sensor L1, L2) is
configured for determination of a supporting force F. The second
sensor system is configured for determination of a towing force
F'.
[0077] Furthermore, the tow couplings according to the embodiment
of FIG. 14 may be equipped with a sensor configuration, which is
known from the load pin in FIG. 8. In other words, the sensors,
which reside in the first and in the second shaft like member 4, 4'
may be sensor configurations, each having four sensors LX1, LX2,
LY1, LY2 having sensing directions, which are substantially
parallel to the shaft axis A and A', respectively. The sensor
configuration, which is shown for a load pin in FIGS. 7 and 8 may
be applied in the tow coupling 30 as well. According to this
particular embodiment of the invention, additional force vectors
may be determined.
[0078] The tow coupling 30 according to the embodiment of FIG. 15
may be equipped with a sensor configuration, which is known from
FIG. 13. In other words, the sensors, which reside in the first and
in the second shaft like member 4, 4' may be sensor configurations,
each having four sensors L1, L2, L1* and L2* having sensing
directions, which are substantially perpendicular to the shaft axis
A and A', respectively. The sensor configuration, which is shown
for the ball joint in FIGS. 12 and 13 may be applied in the tow
coupling 30 of FIG. 15 as well. According to this particular
embodiment of the invention, additional force vectors may be
determined.
[0079] The sensors L1, L2, L1', L2' of the tow coupling 30 are
preferably arranged inside the hollow curved shaft like member 32
of the tow coupling 30.
[0080] The direction sensitive sensors L1, L2, L1', L2', L1*, L2*,
LX1, LX2, LY1, LY2 may be vector sensors. In particular,
Hall-effect, magneto-resistance, magneto-transistor, magneto-diode,
MAGFET field sensor or fluxgate magneto-meter sensors can be
applied. This advantageously applies to all embodiments of the
invention.
[0081] The magneto-elastic sensor according to aspects of the
invention is advantageously applicable for load measurement in
cranes, for overload detection in elevators, for load detection in
farming equipment, for load detection in construction equipment,
for load detection in chassis applications or for load detection in
a fork lifter.
[0082] In addition to this, the magneto-elastic sensor is
advantageously applicable in suspension applications for load
detection, load detection for cable cars, load detection for
railroad applications and load detection for cable forces.
Furthermore, it is applicable for flap load detection, for load
detection in hydraulic cylinders, for structural load detection,
line tension detection, sheave or pulley load detection or shackle
load detection. In addition to this, the magneto-elastic sensor is
advantageously applicable for towing or pulling load detection
and/or for brake force detection.
[0083] The magneto-elastic sensor may be integrated into a hoisting
gear or in a winch, in cable laying equipment, marine tankers or in
offshore platforms. A rope, a chain and/or a brake anchor, bearing
blocks, a pivot and/or a shackle may be provided with the
magneto-elastic sensor according to aspects of the invention.
[0084] A floor conveyor, a sprocket axle, front end loaders,
railroad couplings, conveyor belt rollers, clevis joints, crane
cargo hooks, a tow bar connection, a rail points load pin and/or
connecting rod may include the magneto-elastic sensor according to
embodiments of the invention. The mooring line tension or a tow
line tension may be determined.
[0085] It is understood that a respective one of the mentioned
entities may be advantageously equipped with the sensor according
to aspects of the invention. In particular these entities may
comprise a load pin according to aspects of the invention, this
applies for example to marine or industrial equipment.
[0086] Although certain presently preferred embodiments of the
disclosed invention have been specifically described herein, it
will be apparent to those skilled in the art to which the invention
pertains that variations and modifications of the various
embodiments shown and described herein may be made without
departing from the spirit and scope of the invention. Accordingly,
it is intended that the invention be limited only to the extent
required by the appended claims and the applicable rules of
law.
* * * * *